Contrast enhancement and histopathological findings in vestibular schwannoma.

Changes of contrast uptake are considered to indicate the efficacy of therapy in irradiated vestibular schwannomas. We present a case of a large vestibular schwannoma with heterogeneous contrast uptake on MRI. Using neuronavigation, histological samples were obtained during surgery from an area with homogeneous contrast uptake and from a central tumor portion without contrast enhancement on MRI. Intraoperative investigation found no evidence of necrotic tumor, and histopathological examination revealed an active tumor in both sections, with no central necrosis. This finding illustrates the surgical experience that " necrotic tumor areas " on MRI may not be consistent with intraoperative findings. Lack of contrast uptake in previously irradiated schwannomas may not be indicative of effective radiotherapy.